What does 'intention-to-treat analysis' mean?

What does 'intention-to-treat analysis' mean?

• A. All subjects are analyzed in the groups they were assigned to even if they do not complete the study
• B. Only subjects who complete the study are analyzed
• C. Subjects are analyzed by the treatment they actually receive
• D. Withdrawals are excluded from analysis

Answer: (A)

Intention-to-treat analysis keeps participants in the analysis according to the group they were randomized to, regardless of whether they completed the treatment or adhered to the protocol. This preserves the original randomization, which helps avoid bias that can arise when people switch treatments or drop out. It also gives a sense of how the treatment would work in real life, where not everyone follows instructions perfectly. In practice, researchers still address missing data from withdrawals with appropriate methods, but the core idea remains: analyze by the initial assignment, not by what actually happened. Other approaches—analyzing only those who complete the study or those who actually received the treatment—can bias results and overstate how effective the treatment is, while excluding withdrawals likewise distorts the picture.

Intention-to-treat analysis keeps participants in the analysis according to the group they were randomized to, regardless of whether they completed the treatment or adhered to the protocol. This preserves the original randomization, which helps avoid bias that can arise when people switch treatments or drop out. It also gives a sense of how the treatment would work in real life, where not everyone follows instructions perfectly. In practice, researchers still address missing data from withdrawals with appropriate methods, but the core idea remains: analyze by the initial assignment, not by what actually happened. Other approaches—analyzing only those who complete the study or those who actually received the treatment—can bias results and overstate how effective the treatment is, while excluding withdrawals likewise distorts the picture.